Field
Apparatuses and methods consistent with exemplary embodiments relate to an image processing device and an image processing method, and more particularly, to an image processing device and an image processing method configured to transmit an image signal containing high dynamic range (hereinafter, to be called “HDR”) information as additional information for each scene or frame and to analyze and decode and process the image signal into an image to be displayed by a display device to thereby fully express potential of the display device.
Description of the Related Art
In a natural environment a very wide range of brightness levels are present from, e.g., a very dark scene such as a night sky to a very bright scene such as the light of the sun. Additionally, the natural environment has a wide dynamic range from a very dark portion to a very bright portion in a single scene. However, due to the limitation of maximum brightness and limitation of expressiveness for a transmitted input signal, normal display devices rarely express a dynamic range or corresponding brightness ratio that a human visual system may experience from a real natural environment.
Image producers may produce full high definition (FHD) images or ultra high definition (UHD) images with 10-bit or 12-bit for each pixel with high dynamic range that have been photographed by an image signal generator 12, as shown in FIG. 18, such as a camera. The FHD images or UHD images with HDR that have been produced as above may be converted into a lower number of bits such as 8 bits per pixel by taking into account communication bandwidth or capability of a user's display device. Then, as shown in FIG. 18, the images are encoded by a high efficiency video coding (HEVC) encoder 14 and compressed into an HEVC bit stream for transmission. As shown in FIG. 19, the transmitted HEVC bit stream is received by a bit stream receiver 22, and is decoded by an HEVC decoder 24, and then transmitted to a timing controller 26 and finally displayed by an image output portion 28 such as a display panel. Typically, an 8-bit per pixel image has a narrower dynamic range than a 10-bit or 12-bit per pixel image. Encoding a 10-bit or 12-bit image is expected to significantly increase bandwidth usage. Even if an image with a high bit depth is transmitted, such as 10-bit or 12-bit HDR images, the receiving display device may not properly display the image if the display device is an 8-bit image display device due to the limited expressiveness of such display device.
A display device may have a fixed dynamic range for expressing an input image for each frame. However, an image in a single scene may have a very dark background portion including a particularly bright portion. On the contrary, there may be a case where a particular portion of a very bright image should be displayed very dark.
When a brightness of a particular bright portion of a very dark image is different from a maximum brightness of a very bright image, the image may give a sense of reality similar to the case of how human eyes would experience the scene from viewing the real environment. Even if it is considered that the display device has a limitation in minimum/maximum brightness due to hardware, the display devices fail to provide a user experience factor from a reality aspect that may otherwise be provided to a user.